Cold stress during scotophase elicited differential responses in quail pineal, retinal, and serum melatonin levels.

Effects of cold stress during scotophase on pineal, retinal and serum melatonin levels were examined in quails. All experimental subjects were housed under a constant room temperature of 23 +/- 2 degrees C and a daily 12 h:12 h light:dark cycle. After 1 week of adaptation, quails were exposed to 4 degrees C in darkness for 60, 120, 180 and 210 min. Immediately following their respective cold treatments, subjects were sacrificed at mid-dark and pineal, retina and serum samples were collected for melatonin radioimmunoassay. Cold stress during scotophase was found to potentiate melatonin levels in the retinas significantly. Conversely, cold exposures in dark significantly decreased melatonin levels in pineal glands and serum. Such diversified responses might be attributed to tissue specific variations in adrenergic and/or dopaminergic receptors responsible for regulating the synthesis and/or secretory mechanisms of melatonin.